Plotter system and method of operation

ABSTRACT

A plotter system and its method of operation in which paper or other sheet material is fed from a feed drum, then over a plotter drum to have data recorded thereon in transit, and is then collected on a collecting drum. The paper is held in lateral tension on the plotter drum by having a selected pattern of holes along its longitudinal edges engage corresponding projections on positioning and drive members located at opposite ends of the plotter drum which are continuously biased laterally away from each other to retain the paper in lateral tension.

United States Patent [191 Gerber Dec. 17, 1974 PLOTTER SYSTEM AND METHOD OF OPERATION [75] Inventor: Heinz Joseph Gerber, West Hartford, Conn.

[73] Assignee: The Gerber Scientific Instrument Company, South Windsor, Conn. [22] Filed: Apr. 20, 1973 [21] Appl. No.: 353,116

[52] US. Cl 226/79, 226/179, 226/192 [51] Int. Cl. G03b 1/24 [58] Field of Search ..226/6, 79, 83, 179, 76, 226/192 [56] References Cited UNITED STATES PATENTS 2,630,901 3/1953 Johnson 226/79 3,240,116 3/1966 Stamm 226/79 X Primary Examiner-Richard A. Schacher Attorney, Agent, or FirmMcCormick,'Paulding &

Huber 5 7 ABSTRACT A plotter system and its method of operation in which paper or other sheet material is fed from a feed drum, then over a plotter drum to have data recorded thereon in transit, and is then collected on a collecting drum. The paper is held in lateral tension on the plotter drum by having a selected pattern of holes along its longitudinal edges engage corresponding projections on positioning and drive members located at opposite ends of the plotterdrum which are continuously biased laterally away from each other to retain the paper in lateral tension.

8 Claims, 3 Drawing Figures PATENTEL DU]! 7 I974 3 8 54 44 SHEET 1 [IF 2 RE i DING /|NSTRUMENT STYLUS PLOTTER PAPER i E COLLECTING DRUM DRUM SHEET 2 OF 2 PAIENIE SEC 1 71974 Q m? a E mm QT K PLOTTER SYSTEM AND METHOD OF OPERATION BACKGROUND OF THE INVENTION 1. Field of Invention This invention relates to plotting systems having plotter drums which transport plotting paper thereover at a selected rate and in a flattened condition at all times to have data recorded thereon by a plotting instrument which engages the paper as it passes over the plotter drum, and more particularly, to such a plotter drum in which the plotting paper is held in lateral tension at all times so that it lies perfectly flat against the smooth outer surface of the drum to present the ideal writing surface for the recording instrument.

2. Description of the Prior Art In the plotter drum art, sprocketed paper holders have been used but were laterally or axiallyfixed and could not compensate for variation in the paper width due to temperature, humidity and other factors and the paper had a tendency to bunch and tear during transition'across the outer surface of the plotter drum.

In the prior art,'a plotter drum having two sprocket drive members of fixed lateral spacing has been utilized with plotting paper having laterally extending slots in' one longitudinal edge thereof to engage the sprocket projections and permit relative lateral or axial motion of the paper with respect to-the sprocket, however, the lateral slots-sprocketdrive combination was found to have poor paper holding quality and therefore the paper bunched and tore during the transition of the paper'across the plotter drum and moved when thedata plotting instrument applied recording pressure thereto.

vention, one of the driving members or sprockets is fixed axially with respect to the remainder of the plotter drum while the other is mounted for axial motion with respect thereto and biased axially away from the first drive member or sprocket.

In accordance with a further aspect of the present in- I vention, a holddown member is positioned over the Also in some prior art plotters, an axially floating set of sprockets has been used to accommodate variations in paper dimensions; however, the floating sprockets were incapable stretching the paper tightly in the lat-- eral direction as plotting operations were performed. As a consequence, the same bunching and tearing of the paper was experienced as with axially fixed sprockets.

SUMMARY OF THE INVENTION vide an improved plotter drum system in'which 'two drive members, such as sprockets, are positioned at opposite ends of the plotter drum and are separated axially or laterally, i.e., along the axis of the drum, about the distance of the width of the plotting paper. Projections of selected shape and pattern protrude therefrom so as to engage mating apertures in the longitudinal edges of the plotting paper. The drive members are axially urged away from one another continuously to hold the paper in lateral (axial) tension to prevent bunching' plotting A primary object of the present invention is to propaper on the axially movable drive member, and is mounted to translate axially therewith' so as to provide a holddown force on the paper against the axially movable drive member at all times.

It is a further feature of the present invention that the plotting paper is being held in lateral tension at all times so that there are no deformations in the paper as it passes over the drum, thereby avoiding the plotting inaccuracies caused by such paper deformation, and wherein the writing instrument which 'transcr ibes the data onto the paper may exert force on the paper duringthe recording operation without moving the paper on the drum.

The present invention permits accurate plotting of data onto the plotting paper being passed over the plotting drum because the plotting paper is continuously and automatically held in flat condition against the plotting drum surface and in lateral tension at all times, despite dimensional changes in the plotting paper.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic showing of a plotting systemutilizing my invention.

FIG. 2 is an enlarged, perspective showing of my improved plotter drum.

FIG. 3 is a cross-sectional showing of my improved plotter drum.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 we see a schematic showing of a plotting system 10 utilizing my improved plotting drum. Plotting system 10 includes paper feed drum 12, which is mounted for rotation about its axis 14 and which carries plotting paper 16, a strip of recording material, tightly wound in spool fashion thereon. The plotting paper 16 can be as much as six feet or more in width and, with such size, can vary in width as much as i A inch due to humidity, temperature and other factors when it leaves roll 12. The strip of plotting paper 16 is unreeled from the paper feed drum l2 and then passes over paper plotter drum assembly 18 and is then wound onto paper collector drum 20. Plotter drum assembly 18 is mounted for rotation about axis 22, and collector drum 20 is mounted for rotation about axis 24, each of which is preferably parallel to axis 14.

The system 18 maybe driven in any convenient fashion, such as mating gear sectors 26 and 28, which are mounted for rotation with drum assembly 18 and drum 20, respectively, so that the driving of either gear or drum will cause the two drums to rotate in opposite directions. For example, with gear 28 being driven by a conventional motor 25 in a clockwise direction, it will drive collector drum in a clockwise direction and will drive gear 26 and plotter drum assembly 18 in a counterclockwise direction. It may be desirable to provide no drive for paper feed drum 14 so that it will serve to add inertia to the system to place the paper 16 in longitudinal tension as it passes over plotter drum l8 and is wound onto collector drum 20. In an alternative and preferred form, it may be desirable to connect all three drums 12, 18 and 20 by mating gears, pulleys, or other conventional interconnections so that the plotter drum 18 can be reversibly driven and the recording strip or paper 16 may be provided with slack at each side of the plotter drum to remove all unnecessary loads from the driving connection between the plotter drum 18 and the plotting paper 16. In this form the drums l2 and 20 reverse their feeding and collecting roles with each reversal of the plotter drum rotation. A conventional data recording instrument 30, with conventional stylus, writing instrument or recording head 32 projecting therefrom and controlled thereby, is positioned to impart data or other intelligence onto plotting paper 16 as it passes over plotter drum assembly 18. Utilizing the plotting system 10, it will be obvious to those skilled in the art that on-line data such as temperature, humidity, or pressure or prerecorded data can be received by instrument 30, so as to control stylus 32 and plotter drum 18 to impart that intelligence onto the strip of plotting paper 16 as it passes over plotter drum assembly 18.

While FIG. 1 depicts a simple plotting system, my improved plotter drum assembly 18 can also be used with plotting systems of any sophistication, such as that disclosed in US. Pat. application Ser. No. 88,259, filed Nov. 10, I970 and entitled Method and Apparatus for Transporting aStrip of Recording Material" by Heinz Joseph Gerber and having the same assignee, and to which reference may be had.

Referring to FIG. 2 we see a perspective showing of my plotter drum assembly 18 which is mounted for rotation by conventional means (not shown) about axis 22. Plotter drum assembly 18 comprises basically plotter central portion 40, which is preferably of cylindrical shape and presents a smooth outer surface to the plotting paper 16 passing thereover. Axially fixed drive and positioning member or sprocket 42 is positioned at one end of central portion and is also preferably of cylindrical shape and has a pattern of projections 44 extending therefrom and positioned circumferentially thereabout. Axially translatable drive and positioning member or sprocket 46 is located at the opposite end of central member 40 and is also preferably of cylindrical shape and has a selected pattern of projections 48 projecting therefrom and positioned circumfere ntially thereabout. While two axially spaced rows of equally spaced and'circumferentially oriented projections are shown in both drive members 42 and 46, a single row could have been used or any desired pattern of projections or other paper-to-drum attachment means could have been used. It is an important teaching of my invention that, as best shown in FIG. 2, the plotting paper 16 extends axially beyond both drive members 42 and 46 by a slight amount as it passes in translation over the plotter drum assembly 18 and has a selected pattern of selectively sized holes 50 and 52 along the opposite longitudinal edges thereof which relatively snuggly engage projections 44 and 48 as paper 16 passes over drum assembly 18 so that paper 16 is secured in position and driven with respect to plotter drum assembly 18 as the plotter drum rotates. Drive gear 26 is positioned at one end of plotter drum assembly 18 and serves to drive the drum assembly 18 about its axis 22.

Holddown member 54 is pivotally mounted from rod 56 in conventional fashion so that it may be either pivoted back away from axially movable drive member 46 or may be brought down thereagainst as shown in FIG. 2 to serve to hold or restrain plotting paper I6 in position against drive member 46. Holddown member 54 is mounted on shaft 56 so that it-can translate axially along axis 22 with drive member 46 since it is engaged thereby in a manner to be described in greater particularity hereinafter. Holddown member 54 and its support rod 56 do not rotate with plotter drum assembly 18.

Referring to FIG. 3 we see plotter drum assembly 18 in greater particularity. In FIG. 3, the same reference numerals will be used to describe corresponding parts in FIG. 2. Central portion 40 consists basically of cylindrical member 60, which is fabricated to present a smooth exterior and a preferably cylindrical surface 62 to support the plotting paper 16 during the plotting operation. First drive member or sprocket 42 is connected to cylinder 60 through joined flanges 64 and 66, by means of bolt mechanisms 68 so that drive member 42 is solidly connected to central portion 40 for rotation therewith about axis 22. Drive member 42 could be integral with cylinder 60 but is preferably removably connected thereto. Support shaft 70 is supported in fixed position concentrically about axis 22 and carries antifriction bearings 72 and 74 for supporting the remainder of the plotter drum assembly 18 therefrom for unidirectional or duo-directional rotation about axis 22. The outer race of bearing 72 is pressed into sleeve 76 for rotation therewith, and sleeve 76 is connected at one of its ends in any conventional fashion to cylinder 60 and at its opposite end to end plate 78 by bolt mechanisms 80. The outer race of bearing 74 matingly engages surface of drive member 42 for rotation therewith. Nut 75 cooperates with spacer 81 to position bearing 74 on shaft 70 and spring 83 urges bearing 74 against surface 85 of drive member 42 to axially position the rotatable members of drum 18 on shaft 70. The outboard end of drive member 42 is connected to end plate 82 by conventional connecting means, such as bolt or screw members 84. Drive gear 26 is positioned between surfaces 77 and 79 of members 82 and 42 and bolts 84 pass therethrough to retain drive gear 26 in pinched relationship and fixed position between drive member 42 and end plate 82 for rotation about axis 22.

.Axially movable drive member 46 is positioned between central cylinder 60 and end plate 78 on axially directed rod members 86 and 88, which'are supported at one end by bushing members 90 and 92 in apertures 94 and 96, respectively, of end plate 78. The opposite ends of support rods 86 and 88 are supported in bushings 98 and 100 in apertures in sleeve member 76. Axially movable drive member 46 has apertures 102 and 104 therein which engage support rods 86 and 88 in a pressed fit relationship or by other attachment means and therefore are mounted thereon to translate axially along axis 22 therewith during the plotting operation. Spring members 106 are located in sleeves 108 within cylinder 60 and, with the cooperation of fixed plugs 110 and movable plugs 112, located at opposite ends thereof, serve to cause support shaft 86 and 88 and hence drive member 46 to be continuously urged axially away from central portion 40 by the action of springsl06 bearing against fixed plug 110 and forcing movable plug 112 and the support rods 86 and 88, and therefore drive member 46, axially toward the right shown in FIG. 3. Drive member 46 carries retainer ring 120 therewith and, ring 120 engages groove 122 (see FIG. 2) of holddown member 54 to cause the holddown member 54 to move axially with drive member 46. Holddown member 54 also includes grooves 124 and 126 to receive and permit rotation of the projections 48 of drive member 46. 8

Drive member 42 and drive member 46 are preferably cylindrical in shape and are mounted on opposite axial or lateral sides of cylinder 60 of central portion 40 of plotter drum assembly 18 and are mounted through bearings 72 and 74 on shaft 70 concentrically about axis 22 for rotation thereabout in unison. It will therefore be seen that members 42, 40 and 46 rotate in unison concentrically about axis 22. Central member 40 and drive members 42 and 46 of plotter drum assembly 18 cooperate to define a smooth cylindrical surface 123, against which plotting paper 16 bears in translation over the plotter drum assembly 18.

As best shown in FIG. 3, plotter paper 16 bears against smooth, cylindrical surface 123 of central portion 40, drive member 42 and axially translatable drive member 46 in passing over plotter drum assembly 18 and has selectively sized apertures 50 and 52 therein spaced and sized to relatively snugly engage projections 44 and 48 of drive members 42 and 46, respectively, so

that there is no circumferential or axial slipping between the drive members and the plotting paper 16. Since spring members 106 urge axially movable drive member 46 axially away from member 42 in the FIG. 3 construction. a continuous biasing force serves to hold paper 16 in continuous lateral tension between projections 44 and 48, which lateral tension cooperates with the longitudinal tension imparted to the paper by the roll system of FIG. 1 to hold the paper perfectly flat and in tension against the surface 123 of the plotting drum assembly 18.

It will therefore be seen that with the construction of my improved plotter drum assembly 18, central portion 40 and drive members 42 and 46 are mounted to rotate by their supporting mechanism concentrically about axis 22 and to engage apertures 50 and 52 of the plotting paper ]6 with corresponding projections 44 and 48 of drive members 42 and 46, respectively, and to apply both lateral and longitudinal tension to the plotting paper 16 passing over the drum assembly 18. In this fashion, wrinkles, bunching and deformation of the plotting paper does not occur. As variations occur in the width of the plotting paper, linear or nonlinear, the biased drive member 46 moves axially, in view of the force of springs 106, to accommodate the lateral variations in the paper dimension and thereby maintains lateral tension on paper 16 at all times. Springs 106 and the pin 48-aperture 52 connection between member 46 and paper 16, cooperate to axially locate member 46.

I wish it to be understood that I do not desire to be limited to the exact details of construction shown and described, for obvious modifications will occur to a person skilled in the art.

I claim:

1. A drum for advancing a strip of recording material thereover in a flattened condition comprising:

a first rotatable member having an axis of rotation and first engaging means located about the axis of rotation for engaging the strip of material at one longitudinal edge the strip passes over the drum:

a second rotatable member positioned coaxially of the first member and the axis of rotation and having second engaging means located about the axis of rotation for engaging the strip of recording material at the other longitudinal edge as the strip passes over the drum;

a set of support rods extending between the first and second rotatable members in parallel with the axis of rotation, each rod being fixedly attached to one of the members-and slidably received in the other of the members to allow relative movement of the two members in the axial direction and to couple the members together for simultaneous rotational motions about the axis in unison; and

resilient means interposed between the two rotational members for urging the one member axially away from the other.

2. A drum as defined in claim 1 wherein:

each of the support rods is fixedly attached to the second rotational member and is slidably received in the first member; and

a set of bearings support the first member for rotation about the axis of rotation.

3. A drum as definedin claim 2 wherein:

the resilient means comprises at least one spring interposed between the first rotatable member and a support rod fixedly attached to the second rotatable member.

4. A drum as defined in claim 1 wherein:

the support rods extending parallel to the axis of rotation are in turn supported at their opposite ends in the first rotatable member.

5. A drum as in claim 4 further including bushings mounted in the first rotatable member and receiving the opposite ends of the support rods in sliding relationship. Y

6. A drum as in claim 5 wherein:

the resilient means comprises springs mounted in the first rotatable member and cooperating with the support rods to urge the rods axially in one direction relative to the first member; and

the support rods are connected to move the second rotatable member axially relative to the first rotatable member.

7. A drum as in claim 1 wherein:

the first rotatable member includes a smooth cylindrical support surface on which the strip of recording material may rest.

8. A drum as defined in claim 1 further including a rotational drive member attached to the first rotatable member. 

1. A drum for advancing a strip of recording material thereover in a flattened condition comprising: a first rotatable member having an axis of rotation and first engaging means located about the axis of rotation for engaging the strip of material at one longitudinal edge as the strip passes over the drum: a second rotatable member positioned coaxially of the first member and the axis of rotation and having second engaging means located about the axis of rotation for engaging the strip of recording material at the other longitudinal edge as the strip passes over the drum; a set of support rods extending between the first and second rotatable members in parallel with the axis of rotation, each rod being fixedly attached to one of the members and slidably received in the other of the members to allow relative movement of the two members in the axial direction and to couple the members together for simultaneous rotational motions about the axis in unison; and resilient means interposed between the two rotational members for urging the one member axially away from the other.
 2. A drum as defined in claim 1 wherein: each of the support rods is fixedly attached to the second rotational member and is slidably received in the first member; and a set of bearings support the first member for rotation about the axis of rotation.
 3. A drum as defined in claim 2 wherein: the resilient means comprises at least one spring interposed between the first rotatable member and a support rod fixedly attached to the second rotatable member.
 4. A drum as defined in claim 1 wherein: the support rods extending parallel to the axis of rotation are in turn supported at their opposite ends in the first rotatable member.
 5. A drum as in claim 4 further including bushings mounted in the first rotatable member and receiving the opposite ends of the support rods in sliding relationship.
 6. A drum as in claim 5 wherein: the resilient means comprises springs mounted in the first rotatable member and cooperating with the support rods to urge the rods axially in one direction relative to the first member; and the support rods are connected to move the second rotatable member axially relative to the first rotatable member.
 7. A drum as in claim 1 wherein: the first rotatable member includes a smooth cylindrical support surface on which the strip of recording material may rest.
 8. A drum as defined in claim 1 further including a rotational drive member attached to the first rotatable member. 